Experimental measurements on the two-tone method of fine-time uplink synchronization for FH SATCOM signals

The two-tone method of fine-time uplink synchronization for a frequency-hopped (FH) spread-spectrum satellite communication system was implemented in a hardware-based laboratory experiment using an analog surface acoustic wave spectrum analyzer. The method produces a timing-error estimate. In order to correct the bias and inconsistency in this estimate, a technique called bias reduction is used. Measurements were taken with and without bias reduction. The system was tested under broadband noise jamming with signal-to-noise ratios of 0, 10, and 20 dB, and under tone jamming with a signal-to-jammer ratio of 9 dB. The experimental results show that the method without bias reduction leads to an inconsistent estimator for the actual timing error, whereas the method with bias reduction leads to an inconsistent estimator for the actual timing error. The experimental results from noise jamming tests using the method with bias reduction are compared with simulated results generated from theory